Those who spent their childhood life in rural Kumaun and Garhwal they will be familiar with Dalya Gurus or Aulya Gurus playing Ektara (Single String Musical instrument) while narrating the stories of Bharthari or Gorakh Literature . There is strong reason behind Dalya Gurus or Aulyas Gurus playing Ektara musical instrument and not other instruments while preaching

The following sutra of Vigyan Bhairav is the reason behind uses of Ektara by Dalya/Aulya Gurus

तंत्र्यादीवाद्यमशब्देषु दीर्घेषु क्रमसंस्थिते:

अन्यनचेता: प्रत्यन्ते परव्योमबपुभर्वेत (विज्ञानं भैरव - ४१ )

Shiva Says to Parvati ----- If one listens with undivided attention on sound of string musical instruments and others which are played successively and are prolonged , then one becomes absorbed in supreme ether of consciousness (Vigyan Bhairav or Bhairav Tantra, 41)

As the sutra suggests that when a person focuses on the collective and prolonged sound of string , the person attains Bhairav ( being in present / not with fear of past nor worry of future. The ektara playing becomes the medium of Shaktoupay with just touching Shambhupay

To manufacture sitar etc and travel along with Sitar or Vani etc is difficult the best alternate is Ektara which solves all purposes

Even if you study or experience , you will find that modern music brings playing of string instrument for attracting audience and their attachment to music.